1. Field of the Invention
This invention relates to scanning exposure systems and more particularly to improved methods and apparatus for exposing a workpiece to radiation defining a pattern.
2. Description of Related Art
Disadvantages of the current art are as follows:
a) The field size of a stepper and/or a scanner is limited by the mask size and the lens size.
b) During the manufacture of simply one device, many masks for the various layers of the device are required. Pfauler et al. xe2x80x9cHigh-Throughput Optical Direct
Write Lithographyxe2x80x9d, Solid State Technology (June 1997), pp. 175-176, 178, 180, 182 describes a direct write lithography system using a programmable phase-modulated spatial light modulator (SLM) system in which the image is reflected from the SLM onto a semiconductor wafer. The spatial light modulator comprises an array of rectangular electrodes with a reflective, deformable viscoelastic layer on top. The SLM serves as a plane mirror in an optical system.
Zwart et al., xe2x80x9cPerformance of Step and Scan System for DUV Lithographyxe2x80x9d, SPIE, Vol. 3051, pp. 817-833 and 835 discusses steppers.
Kazuaki Suzuki et al, xe2x80x9cKrF Step and Scan Exposure System Using Higher NA Projection Lensxe2x80x9d, SPIE Vol. 2726 pp. 767-779 discusses step and scan lens performance.
Martain van den Brink, et al, xe2x80x9cStep and Scan and Step and Repeat, a Technology Comparisonxe2x80x9d, SPIE, Vol. 2726, pp. 734-753 discuses lithography systems.
See Cote et al. xe2x80x9cMicrascan(trademark) III-performance of a Third Generation, Catadioptric Step and Scan Lithographic Toolxe2x80x9d SPIE, Vol. 3051, p. 806
U.S. Pat. No. 5,028,939 of Hornbeck for xe2x80x9cSpatial Light Modulator Systemxe2x80x9d shows a SLM.
U.S. Pat. No. 5,063,602 of Peppers for xe2x80x9cImage Correlation Calculation Apparatusxe2x80x9d shows an image correlation calculation apparatus.
U.S. Pat. No. 5,260,154 of Forrest for xe2x80x9cEvaluating Photolithographic Exposuresxe2x80x9d shows a method of evaluating line-width exposures using a film evaluated with a computer.
U.S. Pat. No. 5,539,568 of Lin for xe2x80x9cMethod of Exposing a Light Sensitive Materialxe2x80x9d and U.S. Pat. No. 4,809,341 of Matsui for xe2x80x9cTest method and apparatus for a Reticle or Mask Pattern used in Semiconductor Device Fabricationxe2x80x9d show a methods of photomask testing.
In accordance with the present invention, a xe2x80x9cMask Image Scanningxe2x80x9d (MIS) exposure system is provided. The pattern images in the mask middle partxe2x80x94a slit shifts in a first direction and simultaneously, a workpiece comprising a photoresist coated silicon semiconductor wafer is shifted synchronously in the opposite direction during the period of exposure.
In accordance with this invention, a dynamic mask exposure system and method comprises a scanning support for a workpiece, a source of a beam of exposure radiation, and a transmissive dynamic mask with orthogonally arranged matrices of actuator lines and binary pixel units which are opaque or transparent as a function of control inputs to the actuator lines, the dynamic mask having a top surface and a bottom surface. A control system connected to supply scanning pixel control signals to the actuator lines of a dynamic mask to form a scanning pattern of opaque and transmissive regions. The beam is directed down onto the top surface of the mask. The beam passing through the transparent pixels and projecting a pattern from the mask onto the support where the workpiece is to be located. A diaphragm is provided with a slit therethrough between the source of the beam and the workpiece. The image projected by transmitting the beam through transparent pixel units in the opposite direction from the scanning support and projecting a scanning pattern from the mask onto the support where the workpiece is to be located. The workpiece is driven in a first direction transverse to the beam by the scanning support, and the pixel control signals scan across the transmissive dynamic mask in a direction opposite from the first direction.
Preferably, the control system comprises a computer and a direct access storage device for storing patterning data, and the transmissive dynamic mask comprises a transmissive spatial light modulator.
Preferably, the source of the beam of exposure radiation comprises a collimated beam of light, the source of the beam of exposure radiation comprises a collimated beam of light provided by a set of condenser lenses projecting the collimated beam of light onto the top surface of the mask, and a set of projection lenses projecting the focussing the pattern from the mask onto the support from the bottom surface of the mask.
Preferably, the transmissive dynamic mask comprises a transmissive spatial light modulator.